Accessory Vertebral Artery: An Embryological Review With Translation from Adachi

The vertebral arteries arise from the posterior superior aspect of the bilateral subclavian arteries and course superiorly through the transverse foramina of C1-C6 vertebrae before joining one another along the anterior surface of the pons. Developmental variations during the fourth to sixth weeks of embryonic development may result in the formation of accessory vertebral arteries, i.e., ipsilateral vertebral arteries of dual origin. This anatomical variation is distinct from and often confused with vertebral artery duplications and fenestrations. This article reviews the anatomy and embryology of the accessory vertebral artery with excerpts from Buntaro Adachi's classic text on vascular anatomical variations. Knowledge of accessory vertebral vessels is important during vascular and spinal procedures of the head and neck. Furthermore, these variations have been associated with cerebrovascular pathologies, such as stroke, dissection, and other hemodynamic anomalies.